Bit control for percussive tools



Aug. 31, 1943.- A. a. DECKER, JR 2,328,201

BIT CONTROL FOR PERCUSSIVE TOOLS Filed Nov. 1, 1940 x 7 3mm aZo-nzo QDec/(en Patented Aug. 31, 1943 BIT CONTROL ron rEao ssIvE TOOLS Alonzo G. Decker-,Jra, Baltimore, Md., assignor to The Black and Decker Manufacturing Company, a cor poration of Maryland. t V

1, 1940, SerialNo. 363,811 sciaims. ci. 2-55 's7)@ Application November In the operation of power hammers, particularly thoseof the high power and highfrequen'cy of "impact which is now establishedpractice, the {resulting vibration is excessive and operating handles usually in the form of a transverse arm passage of heat'below that which occurs in the old type of connection.

whereby the' operation of the drill or other bit is directed, are found to be of relatively short life due to crystallization resulting. from the vibration to which they are subjected. Also the direction of the bit by means of the operating handlesnow in use involves the transmission to the hand of theoperatorof the excessive vibration due to the rhighpower and high frequency impact. A further undesirable incidentdue to the use of the prior apparatus is the transmission through theoperating handleto the hands of the operator of the \inthe tool.

heat which is generated The result of the vibration and heat thus *trjansmitted to and through the handle to the hand of the operator iSjOf primary importance tin-its efiect onthe operator made apparent by weariness andloss of accuracy and efiiciencyin directing the tool, thus affecting adversely-the quality and efliciency of all operationsperformed 1 tinder these conditions. F 'I'he object oi the present invention is to provide an operating handle for directingthe drill or'other bit particularly a connection of the,

"handle to thebitwhichelimiriatesor at least greatly reduces the vibration which is transmitted to the handle and hence to the hand of the operator, thus increasing the life of the operating handle and avoiding harmful weariness l and inconvenience to the operator and particularly loss ofaccuracy and efficiency, as above.

The; operating handle construction and con- 'nectionoi the inventionalso limits and reduces Sthe transmission or l'ieatflfrom the bit to the handle and hence to the hand of the joperato'r.

' Theimproved result attained is largely de-. pendent on the provision in the connection between the operatinghandle'and the bit shank or bit holder shank which, 'for the purposes in hand, are considered identical, -of"a lost motion which in operation gives "relative play to the 4 bitand handle with consequent reduction of the vibratory efiect transmitted to the handle. The :contact betweenthe bit; shank and handle is also reduced Jand rendered intermittent in operation by said lost motion. The invention also con- Fig. 1. h o i p o Fig. '3 is a horizontal sectionon'the lines 33 in Fig'. 1 showing the tool holder shank and In the accompanying drawing, I have illustrated an operating handle embodying the 'features of the invention, the same being adapted for use with drills andsimilar bits for operation by percussive tools as electric and other power hammers, particularly those of the portable type.

- In the drawing: i v I Fig. 1 is a sideelevation of a bit holder and drill bit therein, the same being of the type used withelectric and other portable power hammers the illustration including an operating handle attached directly to the bit holder shank and indirectly to the bit. l i

1 Fig. 2 is asimilar view on a reduced scale of an electric hammer equipped'in accordance with handle and the handle ring in cross section.

. Referring to the drawing by numerals each of which is used to indicate the same or similar parts in the difierent figures, the construction shown comprises autool holder I, having a drill bit Z and an operating handle 3 in their normal operatingrelation. I 3 r The tool holder 1 inthe form shown comprises a-socket member 4 and a shank 5 extending upwardlyfrorn the socket." 'The tail 6 of the bit is seated in the tapered b'ore "I in thesocket 4 andv the socketis provided with-atransverse templates the use ofa resilientcushion'between the connecting members whichboth limits the relative motion and takes up the vibration, and having heat insulating properties reduces the aperture 8 through which a suitable implement may be inserted to loosen the bit. When the bit is thus attached to the holder the bit and holder aref'rigidly connected.

The upper end of the holder shank 5 is reduced at Btofit inthe'nosebf the hammer in accordance with the usual practice." In the form shown, the tool holder shank is shouldered peripherally at In at thebottorn of-said reduced portion 9*, the details abovedes cribed being regular practice.- a

Important difficulties incident to the operation of the prior arttools of this general type are found to be due to the transmission tothe handle and'henc'eto the hands of the operator.

'ofthe vibrations and the heat due to the impact of the. hammer, with the harmful results in the way of the deterioration of the handle by crystallization and loss of efficient control due to wearinessand undue heating. or burning of the hands, as already pointed out. i The present. invention is found to reduce and practically eliminate these dimculties.

An important feature of this invention on which the result attained is largely dependent resides in the provision of a connection oi the operating handle to the bit either directly or edge of the sleeve 25 at 26 is then rolled inwardly into the groove 24% and against the shoulder 22,

or prevent transmission of vibration due to the hammer impact, and to similarly reduce or pre vent the passage of heat by conduction from the bit to the handle and hence to the hand of the operator. i

To this end the tool holder orshank which is rigidly attached to the bit is provided at any suitable point, most conveniently above the socket 4 with a series of splines l2 and intermediate grooves M between the splines, which, in the form :shown, are substantially parallel to the axis of the holder and bit. c

. For .co-operation with the tool holder and particularly the splines I2 and grooves M the draw- ,ingshows the handle 3 provided at its inner end witl'i aring portion l5 which encloses or encircles the tool holder shank immediately above the socket member 4, said ring I5 having its central aperture IEforrned with alternate inwardly disposed splines. I! and grooves it which receive and enter respectively the splines 12 and'grooves M on and in the shank 5. It is important that I there is considerable clearance at IS, IS, IS)" between ring 15 and holder I and particularly between the interengaging splines of the ring and. holder and as a consequence there is a considerable lostmotion between the handle and the holder and the bit therein sothat the handle isnot in any sense rigidwith the'tool holder 1' or with the bit 2. The engagement is, however, suiiiciently positiveto give accurate direction of the bit by the'handle and accurate placement and direction of the holesor other work, with reduction and breakage of contact between the bit and holder in operation.

The splines 82 on the tool holder are in the preferred form of theinvention shown of not much greater axial length than the width of ring l5 and there is a washer orother suitable ring 28 which fits down over the shank 5 of the tool .holderandrests on the top of the splines l2 or on any-suitable stop, being secured in a manner to be described or in any suitable manner, and

serving as astop for the handle.

In the form shown in Fig. l, the tool holder is provided beneath the handle ring 15 with a shoulder 2! formed at the upper end of the socket or otherwise positively related to the shank and the s ace between the bottom of the washer, 29 and the top of the shoulder 2! is greater than the width of'thehandle ring l5. providing for vertical as well-as lateral-and rotary play of the handle 3 relative to the bit 2 and/or bit holder l and vice versa. v

A convenient. manner of securing the stop ring is as follows:

In the form shown in Fig. 1 the tool holder shank 5 is provided with a peripheral abutment 22 at a convenient point spaced above'the splines 12 and the tool holder 5 is to best advantage peripherally grooved at itimmediately below to failure of the handle by greatly reduced.

completing the assembly of the handle and tool holder, the specific details being subject to variation.

While the connection of the handle to the bit holder 01 bit is sufiiciently positive to give the desired control of the later for. accurate work,

bit 2 is thus permitted to have a limited movement up and down or axially and relatively to the handle and there is also a sufficient degree of lost motion or lateral and/or rotative yielding of the'bit relatively to the handle so that contact between the bit or holder and the handle is greatly reduced there being no continuous and positive contact between the handle ring E5 of handle 3 and the bit 2 and/or tool holder I and the vibrations are mainly independent of the handle. Consequently, the tendency to the transmission of vibration and heat from the bit through;the handle to the hand of the operator resulting. in discomfort, weariness and loss of 'eiiiciency on the part of the operator is greatly reduced or almost entirely prevented and with reduction of vibration of the handle the tendency crystallization is I Fig. 2 shows the handle 3- and tool or bit holder 5 and bit 2 assembled in operative relation with an electric hammer 2i. I

The operation will be clear from the preamble and the description of the figures.

- What I claim as new and desire to secure by Letters Patent is: j p d r l. The combination with a bit holder for operation in impact transmitting relation to and with power hammer bit, of an operating handle elongated "transversely to the length of the bit,

' said handle having an apertured portion enclosthe abutment 22. In passing the ring 28 downing said bit holder and a bit controlling connection between the said enclosing portion andthe bit holder, said connection comprising co-oper- 'ating splines and grooves inwardly disposed on the said enclosing portion and outwardly disposed splines and grooves on said bit holder, said splines and grooves on the enclosing portion and onthe bit holder being arranged in inter-engaging relation andhaving an excess of clearance radially and circumferentially, said holder having an upwardly disposed shoulder below the enclosing portion to supportthe handle on the holder, said holder also having a sleeve encircling the same and removably secured thereto above said enclosing portion and a ring encircling said holder above said enclosing portion, and engaged on one sideby the lower end of said sleeve and on I the other side by said enclosing portion, wherebythe holderis supported on the handle. 2. The combination with a. bit socket member for operation in impact transmitting. relation, to and with a power hammer. bit, oi operating handle elongated transversely to the axis of the bit and socket member,- said handle having an 'apertured portion enclosing said bit socket member and a bit controlling connection between said enclosing "portion'and the bit socket; member, said connection comprising co-operating'splines and grooves on the said enclosingpcrtion :and

said bit socket member respectively,said splines and grooves on the socket member andenclosing portion respectively having an excess clearance at other times the socket membermay be ported on the handle one of the abutment means being removable and both said abutment means being supported on the socket, the cooperating surfaces between the abutment means being parallel to the axis of the socket member, and the abutment means being separate from the handle structure.

sup-

3. The combination with a bit holder for operation inimpact transmitting relation to and with 10 apower hammer bit, of an operating handle elongated transversely to the axis 01 the bit and holder, said handle having an apertured portion enclosing said bit holder and a bit controlling connection between said enclosing portion and the bit holder, said connection comprising cooperating splines and grooves on the said enclosing portion and said bit holder respectively, said splines and grooveshaving an excess clearance radially and circumferentially, and abutment means on said holder above and below said enclosing portion, thereby the handle may be at times supported on the holder and at other times the holder may be supported on the handle, one said abutment beinglin the form of a shoulder, a sleeve encircling the holder and supporting said shoulder, said sleeve being removably'engaged with and secured to'said holder to provide for convenient attachment and removable of the handle.

" lonzo G. DECKER, JR. 

